Tetradrachm (Coin) Depicting the Goddess Athena

From the Art Institute of Chicago record

The use of coins as a form of money was invented in western Asia Minor in the early 7th century BCE. At the time when the coins in this case were struck, Greece was made up of separate city-states that issued their own currency. Made of gold, silver, bronze, and electrum (a gold-silver alloy), coins were literally worth their weight, but their value varied according to the percentage of their precious metal content. Occasionally a city needed more money than it had in reserves. By reducing the amount of precious metal and substituting a base metal, a coin could be produced of the same weight but no longer of the same value. Some currency was only honored within its own city walls, but trustworthy money encouraged trade. Athens had the biggest economy, and its coin became the standard in the Greek world.The population was largely illiterate, but it could identify the place of origin of a coin by its imagery. Many of these images referred to myths that were associated with the history of the community and thus were well known to the populace from religious ceremonies and theatrical entertainment. The story of a city’s founding, a local hero, the city’s guardian deity, and even the reason for the city’s wealth were subjects for a coin’s insignia. The emblems chosen to represent an ancient city often related to its patron god or goddess. For instance, the deity might be associated with a new community’s origins or involved in a notable story connected to the city. The most famous of all civic badges was the profile of Athena, the tutelary goddess of Athens, stamped on the city’s coinage. While other cities modernized the looks of their coins, Athens retained this design, first used in about 520 BCE, to emphasize the dependability of its currency. With silver extracted from local mines, the city had a constant source of revenue for financing civic projects such as building a navy or rebuilding after the city was destroyed by the Persians in 480 BCE. The purity and stability of Athens’s coinage made it the standard throughout the Mediterranean for centuries.